Remodeling method of combined cycle plant, distribution duct, and combined cycle plant

ABSTRACT

Provided is a remodeling method of a combined cycle plant including gas turbines; heat recovery steam generators provided corresponding to number of the gas turbines and configured to recover heat of flue gas discharged from the gas turbines and produce steam by the recovered heat; ducts configured to guide the flue gas from the gas turbines toward the respective heat recovery steam generators; and a steam turbine configured to be rotationally driven by the steam produced by the heat recovery steam generators. The remodeling method of a combined cycle plant includes: removing gas turbines and ducts; installing, in place of the two gas turbines, a new gas turbine that is higher in efficiency and smaller in number than the two gas turbines; and installing, in place of the ducts, a distribution duct configured to distribute and guide flue gas from the new gas turbine to two heat recovery steam generators.

TECHNICAL FIELD

The present invention relates to a remodeling method of a combined cycleplant including a gas turbine and a steam turbine, a distribution duct,and a combined cycle plant.

BACKGROUND ART

As a combined cycle plant, there is known a multi-shaft combined cyclepower plant having what is called a 2-on-1 configuration, in which twogas turbine units and a single steam turbine facility are combined (see,for example, Patent Literature 1). In the multi-shaft combined cyclepower plant, a gas turbine unit includes a gas turbine and a heatrecovery steam generator configured to produce steam by heat dischargedfrom the gas turbine, and one heat recovery steam generator is providedfor each gas turbine.

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Patent Application Laid-open No.2003-254011

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

Efficiency of combined cycle plants (CC efficiency) has been improvingyear by year. CC efficiency of old combined cycle plants decreasesrelatively, resulting in low economic efficiency. Thus, even when theproduct durability of old combined cycle plants is left, the operatingrate decreases and economic loss increases. It is conceivable to installa new combined cycle plant having high CC efficiency in order toincrease the economic efficiency, but the cost for newly installing thefacility is large.

An object of the present invention is to provide a remodeling method ofa combined cycle plant, a distribution duct, and a combined cycle plant,which are capable of improving CC efficiency while suppressing increasein cost by using an existing facility.

Means for Solving Problem

The present invention provides a remodeling method of a combined cycleplant. The combined cycle plant includes: a plurality of gas turbines; aplurality of heat recovery steam generators that are providedcorresponding to the number of the gas turbines and configured torecover heat of flue gas discharged from the gas turbines and producesteam by the recovered heat; a plurality of ducts configured to guidethe flue gas from the gas turbines toward the respective heat recoverysteam generators; and a steam turbine configured to be rotationallydriven by the steam produced by the heat recovery steam generators. Theremodeling method includes: a removal step of removing the gas turbinesand the ducts; a gas turbine installation step of installing, in placeof the gas turbines, a new gas turbine that is higher in efficiency andsmaller in number than the gas turbines; and a distribution ductinstallation step of installing, in place of the ducts, a distributionduct configured to distribute and guide the flue gas from the new gasturbine to the heat recovery steam generators.

With this configuration, a new gas turbine having high efficiency isinstalled in place of existing gas turbines, and hence CC efficiency canbe improved. Even when the number of the new gas turbines is smallerthan the number of the existing gas turbines, flue gas is distributed bythe distribution duct, and hence the flue gas can be supplied to theexisting heat recovery steam generators. In this manner, by usingexisting heat recovery steam generators and an existing steam turbineand replacing existing gas turbines with a new gas turbine, the CCefficiency can be improved while suppressing increase in remodelingcost.

It is preferred that the gas turbine installation step be performedafter the removal step, and that the gas turbine installation stepinclude installing the new gas turbine in a former site of the gasturbines removed at the removal step.

With this configuration, the former site of the removed existing gasturbines is a space suitable for installing a gas turbine, and hence thenew gas turbine can be appropriately installed.

It is preferred that the gas turbine installation step be performedbefore the removal step, and that the gas turbine installation stepinclude installing the new gas turbine in a vacant site.

With this configuration, the existing gas turbines can be operated, andhence the plant can be operated, until the removal step is performed.The gas turbine installation step is completed before the removal stepis started, and hence the operation of the plant can be restarted byperforming the removal step and the distribution duct installation step.Consequently, an operation suspension period of the plant due toremodeling can be shortened.

It is preferred that each of the heat recovery steam generators be avertical heat recovery steam generator in which the flue gas flows froma lower side to an upper side in a vertical direction, and that at thedistribution duct installation step, pre-remodeling connection positionsat which the ducts before remodeling are connected to the heat recoverysteam generators and post-remodeling connection positions at which thedistribution duct after remodeling is connected to the heat recoverysteam generators be different positions.

With this configuration, when the heat recovery steam generators arevertical heat recovery steam generators, the distribution duct can beconnected to the post-remodeling connection position different from thepre-remodeling connection position. Consequently, the post-remodelingconnection position can be set to such a position as to facilitate therouting of the distribution duct and the connection of the distributionduct.

It is preferred that the removal step include further removing the heatrecovery steam generators, and that the remodeling method furtherinclude: a heat recovery steam generator installation step ofinstalling, in place of the heat recovery steam generators, a new heatrecovery steam generator provided corresponding to the number of the newgas turbines; and in place of the distribution duct installation step, aduct installation step of installing a duct configured to guide the fluegas from the new gas turbine to the new heat recovery steam generator.

With this configuration, a new heat recovery steam generator having highefficiency is installed in place of existing heat recovery steamgenerators, and hence CC efficiency can be further improved. The numberof the new gas turbines and the number of the new heat recovery steamgenerators can be set to be equal to each other, and hence the flue gasis not required to be distributed. In this manner, by using an existingsteam turbine, replacing existing gas turbines with a new gas turbine,and replacing existing heat recovery steam generators with a new heatrecovery steam generator, the CC efficiency can be further improvedwhile suppressing increase in remodeling cost.

It is preferred that the distribution duct installed at the distributionduct installation step be provided with a cooling device configured tocool the flue gas discharged from the new gas turbine.

With this configuration, the temperature of the flue gas discharged fromthe new gas turbine can be decreased by the cooling device.Specifically, the new gas turbine is higher in efficiency than analready-installed old gas turbine, and the temperature of flue gasdischarged from the gas turbine having high efficiency is higher thanthat of the existing old gas turbine. The existing heat recovery steamgenerator is designed based on the existing old gas turbine, and henceif the existing heat recovery steam generator receives flue gas at hightemperature, the existing heat recovery steam generator may be burntout. Consequently, by cooling the flue gas by the cooling device, theburnout of the existing heat recovery steam generator due to heat of theflue gas can be suppressed. Examples of the cooling device include ablower fan configured to send air by taking in outside air, an ejectorconfigured to take in outside air, and a heat exchanger such as a gascooler, but are not limited thereto.

It is preferred that the combined cycle plant be a multi-shaft combinedcycle plant in which a rotating shaft of the gas turbine and a rotatingshaft of the steam turbine are separate from each other.

With this configuration, the gas turbine can be replaced while leavingthe steam turbine.

The present invention provides another remodeling method of a combinedcycle plant. The combined cycle plant includes: a plurality of gasturbines; a plurality of heat recovery steam generators that areprovided corresponding to the number of the gas turbines and configuredto recover heat of flue gas discharged from the gas turbines and producesteam by the recovered heat; a plurality of ducts configured to guidethe flue gas from the gas turbines toward the respective heat recoverysteam generators; and a steam turbine configured to be rotationallydriven by the steam produced by the heat recovery steam generators. Theremodeling method includes: a removal step of removing one or more ofthe gas turbines and removing the ducts while leaving at least one ofthe gas turbines; a gas turbine installation step of installing, inplace of the removed gas turbines, a new gas turbine that is higher inefficiency than the removed gas turbines; and a distribution ductinstallation step of installing, in place of the ducts, a distributionduct configured to merge the flue gas from the left gas turbine and theflue gas from the new gas turbine together, and distribute and guide themerged flue gas to the heat recovery steam generators.

With this configuration, CC efficiency can be improved by installing anew gas turbine having high efficiency in place of one or more existinggas turbines while leaving at least one existing gas turbine. Even whenthe new gas turbine and the existing gas turbine are used incombination, the distribution duct merges the flue gas and distributesthe merged flue gas, and hence the flue gas can be supplied to theexisting heat recovery steam generators. By using the new gas turbineand the existing gas turbine in combination, the flue gas to be suppliedto the existing heat recovery steam generators can be prevented frombeing insufficient. Consequently, the existing heat recovery steamgenerators can produce an amount of steam equivalent to that beforeremodeling, and the output decrease of the steam turbine can besuppressed. In this manner, by using existing heat recovery steamgenerators and an existing steam turbine and replacing one or moreexisting gas turbines with a new gas turbine, the CC efficiency can beimproved while suppressing increase in remodeling cost. Specifically,the total of output of the new gas turbine and output of the existinggas turbine can be increased while maintaining the output of the steamturbine before and after remodeling, and hence the output of the entirecombined cycle plant can be increased.

The present invention provides a distribution duct for connecting one ormore gas turbines to a plurality of heat recovery steam generators thatare larger in number than the gas turbines. The heat recovery steamgenerators are configured to recover heat of flue gas discharged fromthe gas turbines and produce steam by the recovered heat. Thedistribution duct includes: an upstream duct which is connected to thegas turbine and in which the flue gas from the gas turbine flows; and aplurality of downstream ducts which communicate to the upstream duct,branch off from the upstream duct, and are connected to the heatrecovery steam generators to distribute the flue gas flowing through theupstream duct.

With this configuration, even when the number of gas turbines becomessmaller than the number of heat recovery steam generators due toremodeling and the like, flue gas from the gas turbine can bedistributed and supplied to the heat recovery steam generators.

It is preferred that the distribution duct further include a coolingdevice configured to cool the flue gas from the gas turbine.

With this configuration, when the temperature of the flue gas dischargedfrom the gas turbine is high, the flue gas is cooled by the coolingdevice. Consequently, the burnout of the heat recovery steam generatordue to heat of the flue gas can be suppressed.

It is preferred that an allowable temperature of the flue gas and anallowable flow amount of the flue gas, which are allowed by the heatrecovery steam generator, be designed in advance, and that the coolingdevice be configured to cool the flue gas such that a temperature of theflue gas flowing into the heat recovery steam generator becomes equal toor lower than the allowable temperature and that a flow amount of theflue gas flowing into the heat recovery steam generator becomes equal toor lower than the allowable flow amount.

With this configuration, the flue gas that is allowable on design can becaused to flow into the heat recovery steam generator, and hence theinfluence of the flue gas on the heat recovery steam generator can besuppressed.

It is preferred that the cooling device be a blower fan that suppliesoutside air into the distribution duct.

With this configuration, outside air is supplied to the flue gas, andhence the temperature of the flue gas can be easily decreased. Specificexamples of the blower fan include a forced draft fan (FDF).

It is preferred that the blower fan supply the outside air in adirection opposed to a flowing direction of the flue gas.

With this configuration, the mixing of the outside air and the flue gascan be promoted, and hence an uneven heat distribution of the flue gasflowing into the heat recovery steam generators can be suppressed.

It is preferred that the blower fan be provided on an upstream side of abranch portion at which the upstream duct branches into the downstreamducts.

With this configuration, the outside air and the flue gas can be mixedin the downstream duct, and hence the mixing of the outside air and theflue gas can be further promoted.

It is preferred that the distribution duct further include a diffusionmember configured to diffuse the outside air supplied from the blowerfan inside the distribution duct.

With this configuration, the diffusion member can diffuse the outsideair to be supplied into the duct, and hence the mixing of the outsideair and the flue gas can be further promoted.

It is preferred that the cooling device be an ejector configured to takein the outside air by the flue gas flowing inside the distribution duct.

With this configuration, the outside air can be supplied to the flue gasto easily decrease the temperature of the flue gas.

It is preferred that the upstream duct and the downstream ducts areshaped to distribute the flue gas from the gas turbine equally to theheat recovery steam generators.

With this configuration, the flue gas can be equally distributed to theheat recovery steam generators, and hence the flue gas can be preventedfrom being excessively supplied to the heat recovery steam generators.

It is preferred that the upstream duct and the downstream ducts areshaped to be bilaterally symmetric about a flowing direction of the fluegas discharged from the gas turbine.

With this configuration, the upstream duct and the downstream ducts havea bilaterally symmetric shape, and hence the flue gas can be easilyequally distributed.

It is preferred that the downstream ducts have different channel lengthsfrom the upstream duct to the heat recovery steam generator, and that achannel area of a channel through which the flue gas flows from theupstream duct into one of the downstream ducts having a larger channellength be smaller than a channel area of a channel through which theflue gas flows from the upstream duct into one of the downstream ductshaving a shorter channel length.

With this configuration, even when the downstream ducts have differentchannel lengths, the flue gas flowing through the downstream ducts canbe equally distributed.

It is preferred that the distribution duct further include a variabledamper configured to adjust a distribution amount of the flue gas to bedistributed from the gas turbine to the heat recovery steam generators.

With this configuration, irrespective of the shape of the duct, the fluegas can be equally distributed by the variable damper.

It is preferred that the distribution duct further include a channelresistance member configured to adjust a channel resistance in at leastone of the upstream duct and the downstream ducts.

With this configuration, the channel resistance member can adjust theflow of the flue gas in the duct to suppress a drift of the flue gas.

The present invention provides another distribution duct for connectinga plurality of gas turbines to a plurality of heat recovery steamgenerators. The heat recovery steam generators are configured to recoverheat of flue gas discharged from the gas turbines and produce steam bythe recovered heat. The distribution duct includes: a plurality ofupstream ducts which are connected to the gas turbines and in which theflue gas from the gas turbines flows; a merging portion whichcommunicates to the upstream ducts and at which the flue gases flowingthrough the upstream ducts merge; and a plurality of downstream ductswhich communicate to the merging portion, branch off from the mergingportion, and are connected to the heat recovery steam generators todistribute the flue gas flowing through the merging portion.

With this configuration, even when a new gas turbine and an existing gasturbine coexist due to remodeling and the like, flue gas from the newgas turbine and flue gas from the existing gas turbine can be mixed andthereafter the mixed flue gas can be distributed and supplied to heatrecovery steam generators.

The present invention provides a combined cycle plant, including: one ormore gas turbines; the above-mentioned distribution duct, which isconnected to the gas turbine; a plurality of heat recovery steamgenerators that are connected to the distribution duct and larger innumber than the gas turbine; and a steam turbine configured to berotationally driven by steam produced by the heat recovery steamgenerators.

With this configuration, even when the number of gas turbines becomessmaller than the number of heat recovery steam generators due toremodeling and the like, flue gas from the gas turbine can bedistributed and supplied to the heat recovery steam generators. The newgas turbine having high efficiency is installed as a gas turbine, andhence CC efficiency can be improved. In this manner, existing heatrecovery steam generators and an existing steam turbine can be used, andby replacing existing gas turbines with a new gas turbine, the CCefficiency can be improved while suppressing increase in remodelingcost.

The present invention provides another combined cycle plant, including:a plurality of gas turbines having different efficiencies; theabove-mentioned distribution duct, which is connected to the gasturbines; a plurality of heat recovery steam generators connected to thedistribution duct; and a steam turbine configured to be rotationallydriven by steam produced by the heat recovery steam generators.

With this configuration, even when a new gas turbine and an existing gasturbine coexist due to remodeling and the like, flue gas from the newgas turbine and flue gas from the existing gas turbine can be mixed andthereafter the mixed flue gas can be distributed and supplied to heatrecovery steam generators. The new gas turbine having high efficiency isinstalled as a gas turbine, and the existing gas turbine is used incombination, and hence the flue gas to be supplied to the existing heatrecovery steam generators can be prevented from being insufficient.Consequently, the existing heat recovery steam generators can produce anamount of steam equivalent to that before remodeling, and the outputdecrease of the steam turbine can be suppressed. In this manner,existing heat recovery steam generators and an existing steam turbinecan be used, and by replacing existing gas turbines with a new gasturbine, the CC efficiency can be improved while suppressing increase inremodeling cost. Specifically, the total of output of the new gasturbine and output of the existing gas turbine can be increased whilemaintaining the output of the steam turbine before and after remodeling,and hence the output of the entire combined cycle plant can beincreased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram illustrating the arrangement of a GTCCpower plant before remodeling according to a first embodiment;

FIG. 2 is an explanatory diagram illustrating a system of the GTCC powerplant before remodeling according to the first embodiment;

FIG. 3 is an explanatory diagram illustrating an example of thearrangement of a GTCC power plant after remodeling according to thefirst embodiment;

FIG. 4 is a perspective view of a distribution duct in the GTCC powerplant illustrated in FIG. 3;

FIG. 5 is an explanatory diagram illustrating a remodeling method of theGTCC power plant according to the first embodiment;

FIG. 6 is an explanatory diagram illustrating an example of thearrangement of a GTCC power plant after remodeling according to a secondembodiment;

FIG. 7 is an explanatory diagram illustrating a part of a distributionduct where outside air diffusion pipes are installed;

FIG. 8 is a sectional view of the outside air diffusion pipes;

FIG. 9 is a front view of a distribution duct in the GTCC power plantillustrated in FIG. 6;

FIG. 10 is a perspective view of the distribution duct in the GTCC powerplant illustrated in FIG. 6;

FIG. 11 is an explanatory diagram illustrating another example of thearrangement of a GTCC power plant after remodeling according to thesecond embodiment;

FIG. 12 is a plan view of a distribution duct in the GTCC power plantillustrated in FIG. 11;

FIG. 13 is an explanatory diagram illustrating a remodeling method ofthe GTCC power plant according to the second embodiment;

FIG. 14 is an explanatory diagram illustrating a remodeling method of aGTCC power plant according to a third embodiment;

FIG. 15 is an explanatory diagram illustrating an example of thearrangement of a GTCC power plant after remodeling according to a fourthembodiment;

FIG. 16 is a perspective view of a distribution duct in the GTCC powerplant illustrated in FIG. 15; and

FIG. 17 is an explanatory diagram illustrating a remodeling method ofthe GTCC power plant according to the fourth embodiment.

BEST MODES OF CARRYING OUT THE INVENTION

Embodiments of the present invention are described in detail below withreference to the drawings. The present invention is not limited by theembodiments. Components in the following embodiments include componentsthat can easily be replaced by a person skilled in the art orsubstantially the same components. The components described below can becombined as appropriate, and when there are embodiments, the embodimentscan be combined as well.

First Embodiment

FIG. 1 is an explanatory diagram illustrating the arrangement of a GTCCpower plant before remodeling according to a first embodiment. FIG. 2 isan explanatory diagram illustrating a system of the GTCC power plantbefore remodeling according to the first embodiment.

As illustrated in FIG. 1 and FIG. 2, examples of a plant to which aremodeling method of a combined cycle plant according to the firstembodiment is applied include a multi-shaft gas turbine combined cycle(GTCC) power plant (hereinafter referred to as “GTCC power plant”). AGTCC power plant 100 illustrated in FIG. 1 and FIG. 2 is a plant beforeremodeling.

As illustrated in FIG. 1 and FIG. 2, the GTCC power plant 100 beforeremodeling includes a plurality of (two in the first embodiment) gasturbines 10, a plurality of (two in the first embodiment) heat recoverysteam generators 20, a single steam turbine 30, a condenser 40, a watersupply pump 50, and a controller 60. The GTCC power plant 100 has whatis called a 2-on-1 configuration, which includes two gas turbines 10 anda single steam turbine 30. The GTCC power plant 100 is a multi-shaftcombined cycle in which rotating shafts (rotors 14 described later) ofthe two gas turbines 10 and a rotating shaft (rotor 32 described later)of the steam turbine 30 are separate from each other.

The two gas turbines 10 are provided adjacent to each other asillustrated in FIG. 1. As illustrated in FIG. 2, each gas turbine 10 hasa compressor 11, a combustor 12, and a turbine 13. The compressor 11takes in air from an air introduction line La, and compresses the air toobtain high-temperature and high-pressure compressed air.

The combustor 12 supplies fuel to the compressed air supplied from thecompressor 11 through a compressed air supply line Lb to performcombustion. A fuel supply line Ld is connected to the combustor 12. Thefuel supply line Ld supplies fuel to the combustor 12.

The turbine 13 rotates with high-temperature and high-pressurecombustion gas supplied from the combustor 12 through a combustion gassupply line Lc. The turbine 13 is coupled to the rotor 14 and a driveshaft 15. The rotor 14 and the drive shaft 15 rotate along with therotation of the turbine 13. The drive shaft 15 is connected to agenerator G1. The generator G1 converts rotation energy of the driveshaft 15 into electric energy, and outputs the electric energy. Theturbine 13 discharges combustion gas (flue gas) having been used for therotation.

The two heat recovery steam generators 20 are provided adjacent to eachother as illustrated in FIG. 1. Two ducts 17 are provided in parallel,each between one gas turbine 10 and one heat recovery steam generator20. Flue gas discharged from the turbine 13 in the gas turbine 10 flowsthrough the duct 17. Each of the ducts 17 guides the flue gas from eachcorresponding gas turbine 10 to each corresponding heat recovery steamgenerator 20.

Each of the heat recovery steam generators 20 exchanges heat with fluegas flowing therein from each corresponding duct 17, and recovers heatof the flue gas to produce steam. As the heat recovery steam generator20, for example, a vertical heat recovery steam generator 20 is applied.Flue gas is supplied to the vertical heat recovery steam generator 20from the lower side in the vertical direction, and the supplied flue gasflows to the upper side in the vertical direction.

As illustrated in FIG. 2, the heat recovery steam generator 20discharges the produced steam to a main steam line L1. The heat recoverysteam generator 20 is a heat exchanger having a heat transfer pipe L0.Feed water flows inside the heat transfer pipe L0 as a heat medium. Theheat recovery steam generator 20 exchanges heat between the feed waterflowing inside the heat transfer pipe L0 and the flue gas flowingoutside the heat transfer pipe L0 from the lower side to the upper sidein the vertical direction, thereby heating the feed water to producesteam. The heat transfer pipe L0 connects a condensate line L3 and themain steam line L1 to each other. Each of the heat recovery steamgenerators 20 discharges the flue gas having been subjected to heatexchange to a flue gas line L4. A stack 25 is connected to the flue gasline L4. The flue gas discharged to the flue gas line L4 is dischargedto the atmosphere through the stack 25.

The steam turbine 30 is connected to the main steam line L1. The steamturbine 30 has a turbine 31 and a rotor 32. The turbine 31 is rotated bysteam supplied from the heat recovery steam generator 20 through themain steam line Ll. The rotor 32 is rotated by the rotation of theturbine 31. The rotor 32 is connected to a generator G2. The generatorG2 converts rotation energy of the rotor 32 into electric energy, andoutputs the electric energy. The turbine 31 discharges steam having beenused for the rotation to a discharge line L2.

The condenser 40 is connected to the discharge line L2. The condenser 40condenses moisture in the steam supplied from the discharge line L2 toproduce condensate. The condenser 40 discharges the produced condensateto the condensate line L3. The condensate line L3 is connected to theabove-mentioned heat transfer pipe L0. Thus, condensate (feed water)supplied from the condensate line L3 flows through the heat transferpipe L0.

The water supply pump 50 is provided in the condensate line L3. Thewater supply pump 50 supplies the feed water condensed by the condenser40 to the heat transfer pipe L0 in the heat recovery steam generator 20.

The controller 60 controls the operations of the units in the GTCC powerplant 100. As will be described in detail later, the controller 60controls a variable damper 73 and a blower fan 74 provided to adistribution duct 70 in a GTCC power plant 100 after remodelingdescribed later.

Subsequently, the operation of the GTCC power plant 100 configured asabove is described. In each of the two gas turbines 10, air iscompressed in the compressor 11, the compressed air and fuel are mixedand burnt in the combustor 12, and the turbine 13 is rotated bycombustion gas. The generator G1 generates power by the rotation of theturbine 13. Each of the gas turbines 10 discharges the combustion gashaving been used for the rotation of the turbine 13 to eachcorresponding duct 17 as flue gas.

The flue gas is supplied to the heat recovery steam generator 20 throughthe duct 17. The heat recovery steam generator 20 heats feed water byexhaust heat of the flue gas to produce steam. The steam produced by thetwo heat recovery steam generators 20 is discharged to the main steamline L1 and merges in the main steam line L1. The steam is supplied tothe steam turbine 30 through the main steam line L1.

In the steam turbine 30, the turbine 31 is rotated by the steam suppliedfrom the heat recovery steam generators 20. The generator G2 generatespower by the rotation of the turbine 31. The steam turbine 30 dischargesthe steam having been used for the rotation of the turbine 31, andsupplies the steam to the condenser 40 through the discharge line L2.The condenser 40 condenses moisture in the supplied steam to generatecondensate, and the water supply pump 50 supplies the condensate to theheat recovery steam generators 20 through the condensate line L3.

In this manner, the generators G1 generate power by the operation of thegas turbines 10, and the generator G2 generates power by the operationof the steam turbine 30.

Next, a GTCC power plant 100 after remodeling is described withreference to FIG. 3 and FIG. 4. FIG. 3 is an explanatory diagramillustrating an example of the arrangement of the GTCC power plant afterremodeling according to the first embodiment. FIG. 4 is a perspectiveview of a distribution duct in the GTCC power plant illustrated in FIG.3.

As illustrated in FIG. 3, the GTCC power plant 100 after remodelingincludes a single gas turbine 10 a. Specifically, the GTCC power plant100 after remodeling is obtained by replacing existing two gas turbines10 before remodeling with a new single gas turbine 10 a afterremodeling. In the GTCC power plant 100 after remodeling, a distributionduct 70 is provided in place of the ducts 17.

The new gas turbine 10 a has gas turbine efficiency higher than that ofthe gas turbine 10 before remodeling. In the gas turbine 10 a havinghigh gas turbine efficiency, the temperature of combustion gas is higherand the temperature of flue gas is also higher than those in the gasturbine 10 before remodeling. In the new gas turbine 10 a, the intakeflow amount taken in by the compressor 11 is larger and the exhaust flowamount of flue gas discharged from the turbine 13 is also larger thanthose in the gas turbine 10 before remodeling. The number of the gasturbines 10 a is smaller than the number of the gas turbines 10 beforeremodeling. Thus, the number of the gas turbines 10 a is smaller thanthe number of the existing heat recovery steam generators 20. The gasturbine 10 a has gas turbine efficiency higher than that of the gasturbine 10 before remodeling, but has substantially the sameconfiguration as that of the gas turbine 10 before remodeling and hencedescription thereof is omitted.

As illustrated in FIG. 3 and FIG. 4, the distribution duct 70distributes and guides flue gas discharged from the single gas turbine10 a to the two heat recovery steam generators 20. As illustrated inFIG. 3 and FIG. 4, the distribution duct 70 includes an upstream duct71, two downstream ducts 72, a variable damper 73, and two blower fans74. The two downstream ducts 72 in the distribution duct 70 are eachprovided with one gas flowmeter 76 and one gas thermometer 77. Thevariable damper 73, the two blower fans 74, the gas flowmeters 76, andthe gas thermometers 77 are connected to the controller 60.

The upstream duct 71 is connected to the gas turbine 10 a, and flue gasfrom the gas turbine 10 a flows inside the upstream duct 71. Theupstream duct 71 is formed into a rectangular tubular shape, and guidesthe flue gas toward the two downstream ducts 72.

The two downstream ducts 72 branch off from the upstream duct 71 intotwo, and are connected to the two heat recovery steam generators 20. Thetwo downstream ducts 72 are each formed to have a rectangular tubularshape, and communicate to the upstream duct 71 to guide flue gas fromthe upstream duct 71 toward the two heat recovery steam generators 20.

As illustrated in FIG. 3 and FIG. 4, the upstream duct 71 and onedownstream duct 72 are provided to extend straight from the gas turbine10 a toward one heat recovery steam generator 20. The other downstreamduct 72 branches off from a connection portion between the upstream duct71 and the one downstream duct 72. The other downstream duct 72 isobtained by integrating four portions 72 a to 72 d that are provided inthis order from the connection portion toward the other heat recoverysteam generator 20. The portion 72 a is formed to slightly extend upwardin the vertical direction from the connection portion. The portion 72 bis formed to extend from the portion 72 a in a direction orthogonal tothe direction in which the upstream duct 71 extends. The portion 72 c isformed to slightly extend downward in the vertical direction from theportion 72 b. The portion 72 d is formed to extend from the portion 72 cin a direction parallel to the direction in which the upstream duct 71extends.

The variable damper 73 adjusts the distribution amount of flue gas to bedistributed from the gas turbine 10 a to the two heat recovery steamgenerators 20. As illustrated in FIG. 3 and FIG. 4, the variable damper73 has a turning shaft 81, a blade 82 configured to rotate about theturning shaft 81, and a drive source (not shown) configured to allow theturning shaft 81 to be rotationally driven. The turning shaft 81 isprovided along the wall surface of one downstream duct 72. The blade 82is rotated about the turning shaft 81 to change the channel area of theone downstream duct 72. The drive source is connected to the controller60. The driving of the drive source is controlled by the controller 60to turn the blade 82 about the turning shaft 81.

The two blower fans 74 are provided to the two downstream ducts 72,respectively. Each of the blower fans 74 supplies outside air into thedownstream duct 72 to mix flue gas discharged from the gas turbine 10 aand the outside air, thereby cooling the flue gas. For example, a forceddraft fan (FDF) is applied as each blower fan 74. The two blower fans 74are connected to the controller 60, and the operations thereof arecontrolled by the controller 60.

In each of the heat recovery steam generators 20, the allowabletemperature of flue gas and the allowable flow amount of flue gas thatare allowed are designed in advance. Each of the blower fans 74 iscontrolled by the controller 60 such that the temperature of flue gasflowing into each heat recovery steam generator 20 becomes equal to orlower than the allowable temperature. Each of the blower fans 74 iscontrolled by the controller 60 such that the flow amount of flue gasflowing into each heat recovery steam generator 20 becomes equal to orlower than the allowable flow amount.

The two gas flowmeters 76 are provided to the two downstream ducts 72 onthe downstream side of the blower fans 74, respectively. The gasflowmeter 76 measures the flow amount of flue gas which has been mixedwith outside air and flows into the heat recovery steam generator 20.Each of the gas flowmeters 76 is connected to the controller 60, andoutputs the measured flow amount of the flue gas to the controller 60.

The two gas thermometers 77 are provided to the two downstream ducts 72on the downstream side of the blower fans 74, respectively. The gasthermometer 77 measures the temperature of the flue gas which has beenmixed with outside air and flows into the heat recovery steam generator20. Each of the gas thermometers 77 is connected to the controller 60,and outputs the measured temperature of the flue gas to the controller60.

The controller 60 controls the variable damper 73 based on themeasurement results of the two gas flowmeters 76. Specifically, thecontroller 60 controls the variable damper 73 such that the flow amountsof flue gas measured by the two gas flowmeters 76 are substantially thesame. The controller 60 controls the drive source to rotate the turningshaft 81 and rotate the blade 82 about the turning shaft 81, therebychanging the channel area of one downstream duct 72. Based on themeasurement results of the two gas flowmeters 76, the controller 60controls the drive source such that the flow amount of flue gas flowinginto one downstream duct 72 and the flow amount of flue gas flowing intothe other downstream duct 72 are the same. Thus, the equally distributedflue gases are supplied to the two heat recovery steam generators 20,and the temperatures of steams generated by the two heat recovery steamgenerators 20 are substantially the same. Consequently, steams having asmall temperature difference are supplied to the steam turbine 30 fromthe two heat recovery steam generators 20 through the main steam lineL1.

The controller 60 controls the two blower fans 74 based on themeasurement results of the two gas flowmeters 76 and the two gasthermometers 77. Specifically, the controller 60 controls the two blowerfans 74 such that the flow amounts of flue gas measured by the two gasflowmeters 76 become equal to or lower than the allowable flow amount,thereby adjusting the supply amount of outside air supplied into the twodownstream ducts 72. The controller 60 controls the two blower fans 74such that the temperatures of flue gas measured by the two gasthermometers 77 become equal to or lower than the allowable temperature,thereby adjusting the supply amount of outside air supplied into the twodownstream ducts 72.

Next, a remodeling method of the GTCC power plant 100 according to thefirst embodiment is described with reference to FIG. 5. FIG. 5 is anexplanatory diagram illustrating the remodeling method of the GTCC powerplant according to the first embodiment. The GTCC power plant 100 beforeremodeling is as illustrated in FIG. 1, and the GTCC power plant 100after remodeling is as illustrated in FIG. 3.

As illustrated in FIG. 5, in the GTCC power plant 100 before remodeling,two gas turbines 10 and two heat recovery steam generators 20 areconnected by two ducts 17 (Step S11). First, the two gas turbines 10 andthe two ducts 17 are removed from the GTCC power plant 100 beforeremodeling (Step S12: removal step). After the removal step S12 isimplemented, a new gas turbine 10 a is installed (Step S13: gas turbineinstallation step). At the gas turbine installation step S13, the newgas turbine 10 a is installed at a former site of the gas turbine 10before remodeling removed at the removal step S12.

Subsequently, after the new gas turbine 10 a is installed, thedistribution duct 70 is installed so as to connect the new gas turbine10 a and the two existing heat recovery steam generators 20 to eachother (Step S13: distribution duct installation step). At thedistribution duct installation step S13, the upstream duct 71 in thedistribution duct 70 is connected to the gas turbine 10 a, and the twodownstream ducts 72 are connected to the two heat recovery steamgenerators 20, respectively. A connection position (pre-remodelingconnection position) between the heat recovery steam generator 20 andthe duct 17 before remodeling and a connection position (post-remodelingconnection position) between the heat recovery steam generator 20 andthe downstream duct 72 after remodeling are the same position.

In this manner, in the GTCC power plant 100 after remodeling, a new gasturbine 10 a that is higher in gas turbine efficiency than the gasturbine 10 before remodeling is provided. Even when the number of newgas turbines 10 a is smaller than the number of heat recovery steamgenerators 20, the distribution duct 70 is provided to enable the fluegas discharged from the new gas turbine 10 a to be appropriatelydistributed and guided to the two heat recovery steam generators 20.

As described above, according to the first embodiment, it is onlynecessary to use existing two heat recovery steam generators 20 andexisting one steam turbine 30 and replace existing two gas turbines 10with a new gas turbine 10 a having high efficiency, and hence the CCefficiency can be improved while suppressing increase in remodelingcost.

Further, according to the first embodiment, a former site of the removedexisting two gas turbines 10 is a space suitable to install a gasturbine, and hence the new gas turbine 10 a can be appropriatelyinstalled.

Further, according to the first embodiment, the temperature of flue gasdischarged from the new gas turbine 10 a can be decreased by the blowerfans 74. Consequently, by cooling the flue gas by the blower fans 74,the burnout of the existing heat recovery steam generator 20 due to heatof the flue gas can be suppressed.

Further, according to the first embodiment, the GTCC power plant 100 isa multi-shaft combined cycle, and hence the existing gas turbines 10 canbe removed and replaced with the new gas turbine 10 a while leaving theexisting steam turbine 30.

Further, according to the first embodiment, even when the number of gasturbines 10 a becomes smaller than the number of heat recovery steamgenerators 20 after remodeling, the distribution duct 70 can be used todistribute and supply the flue gas from the gas turbine 10 a to two heatrecovery steam generators 20.

Further, according to the first embodiment, the temperature and the flowamount of flue gas can be decreased to be equal to or lower than theallowable temperature and the allowable flow amount by the blower fans74, and hence the influence of the flue gas on the heat recovery steamgenerators 20 can be suppressed.

Further, according to the first embodiment, by using the blower fans 74to supply the outside air to the flue gas, the temperature of the fluegas can be easily decreased.

Further, according to the first embodiment, the variable damper 73enables the flue gas to be equally distributed, and hence the flue gascan be prevented from being excessively supplied to each of the heatrecovery steam generators 20, and the temperature difference betweensteams generated by the two heat recovery steam generators 20 can bereduced.

In the first embodiment, although the blower fan 74 is used as a coolingdevice configured to cool the flue gas, the cooling device is notlimited to the blower fan 74. For example, an ejector may be used tocool the flue gas discharged from the gas turbine 10 a. Alternatively, aheat exchanger such as a gas cooler may be applied as the coolingdevice. The cooling device is not particularly limited.

In the first embodiment, the pre-remodeling connection position at whichthe duct 17 and the heat recovery steam generator 20 are connected andthe post-remodeling connection position at which the distribution duct70 and the heat recovery steam generator 20 are connected are the sameposition, and hence the heat recovery steam generator 20 is not limitedto a vertical heat recovery steam generator 20, and a horizontal heatrecovery steam generator in which flue gas flows in the horizontaldirection may be applied.

It is conceivable to provide the blower fan 74 in the heat recoverysteam generator 20, but in this case, the outside air and the flue gascannot be appropriately mixed, and the heat distribution of the flue gasmay become uneven. It is therefore preferred to provide the blower fan74 in the distribution duct 70 as in the first embodiment.

Second Embodiment

Next, a GTCC power plant 100 according to a second embodiment isdescribed with reference to FIG. 6 to FIG. 13. In the second embodiment,differences from the first embodiment are described in order to avoidduplicated descriptions, and parts having the same configurations as inthe first embodiment are denoted by the same reference symbols.

FIG. 6 is an explanatory diagram illustrating an example of arrangementof a GTCC power plant after remodeling according to the secondembodiment. FIG. 7 is an explanatory diagram illustrating a part of adistribution duct where outside air diffusion pipes are installed. FIG.8 is a sectional view of the outside air diffusion pipes. FIG. 9 is afront view of the distribution duct in the GTCC power plant illustratedin FIG. 6. FIG. 10 is a perspective view of the distribution duct in theGTCC power plant illustrated in FIG. 6. FIG. 11 is an explanatorydiagram illustrating another example of the arrangement of the GTCCpower plant after remodeling according to the second embodiment. FIG. 12is a plan view of a distribution duct in the GTCC power plantillustrated in FIG. 11. FIG. 13 is an explanatory diagram illustrating aremodeling method of the GTCC power plant according to the secondembodiment.

As illustrated in FIG. 6 and FIG. 11, in the GTCC power plant 100 afterremodeling according to the second embodiment, a single new gas turbine10 a is provided in place of existing two gas turbines 10. In the firstembodiment, the new gas turbine 10 a is installed in the former site ofthe removed existing gas turbine 10, but in the second embodiment, thenew gas turbine 10 a is installed in a vacant site in the GTCC powerplant 100.

Examples of the location to install the new gas turbine 10 a include alocation illustrated in FIG. 6 and a location illustrated in FIG. 11. Inthe following description, first, a case where the new gas turbine 10 ais provided in the location illustrated in FIG. 6 is described. In FIG.6, the new gas turbine 10 a is provided side by side with two heatrecovery steam generators 20, and is provided on one side of the twoheat recovery steam generators 20 (left side in FIG. 6). The new gasturbine 10 a provided in the GTCC power plant 100 after remodeling isthe same as in the first embodiment, and hence description thereof isomitted.

As illustrated in FIG. 6 to FIG. 10, a distribution duct 110 includes anupstream duct 111, two downstream ducts 112, a blower fan 113, andoutside air diffusion pipes 114. Two gas thermometers 117 are providedto the two downstream ducts 112 in the distribution duct 110,respectively. The blower fan 113 and the gas thermometers 117 areconnected to a controller 60.

The upstream duct 111 is connected to the gas turbine 10 a, and flue gasfrom the gas turbine 10 a flows inside the upstream duct 111. Theupstream duct 111 is formed into a rectangular tubular shape, and guidesthe flue gas toward the two downstream ducts 112. The upstream duct 111is obtained by integrating two portions 111 a and 111 b that areprovided in this order from the gas turbine 10 a toward the two heatrecovery steam generators 20. The portion 111 a is formed to extend fromthe gas turbine 10 a in a direction (up-down direction in FIG. 6)orthogonal to the direction in which the two heat recovery steamgenerators 20 are arranged. The portion 111 b is formed to extend fromthe portion 111 a in the direction in which the two heat recovery steamgenerators 20 are arranged. The outside air diffusion pipes 114described later are provided at a bending portion formed by the portion111 a and the portion 111 b.

The two downstream ducts 112 branch off from the upstream duct 111 intotwo, and are connected to the two heat recovery steam generators 20. Thetwo downstream ducts 112 are each formed to have a rectangular tubularshape, and communicate to the upstream duct 111 to guide flue gas fromthe upstream duct 111 toward the two heat recovery steam generators 20.

One downstream duct 112 is connected to the lower surface side of theupstream duct 111, and is provided to extend from the upstream duct 111toward one heat recovery steam generator 20. The one downstream duct 112is parallel to the portion 111 a of the upstream duct 111.

The other downstream duct 112 is obtained by integrating two portions112 a and 112 b that are provided in this order from the upstream duct111 toward the other heat recovery steam generator 20. The portion 112 ais formed to extend from the upstream duct 111 in the direction in whichthe two heat recovery steam generators 20 are arranged. The portion 112b is connected to the lower surface side of the portion 112 a, and isprovided to extend from the portion 112 a toward the other heat recoverysteam generator 20. The portion 112 b is parallel to the portion 111 aof the upstream duct 111 and the one downstream duct 112.

The channel length of the other downstream duct 112 is longer than thechannel length of the one downstream duct 112. The upstream duct 111 andthe two downstream ducts 112 are shaped to distribute flue gas from thegas turbine 10 a equally to the two heat recovery steam generators 20.Specifically, in the two downstream ducts 112, the channel area of achannel through which flue gas flows from the upstream duct 111 into oneof the downstream ducts 112 having a longer channel length is smallerthan the channel area of a channel through which the flue gas flows fromthe upstream duct 111 into one of the downstream ducts 112 having ashorter channel length. In other words, the channel area of the channelthrough which the flue gas flows from the upstream duct 111 into one ofthe downstream ducts 112 having a shorter channel length is the channelarea on the downstream side of the portion 111 b of the upstream duct111. The channel area of the channel through which the flue gas flowsfrom the upstream duct 111 into one of the downstream ducts 112 having alonger channel length is the channel area on the upstream side of theportion 112 a of the downstream duct 112. In the second embodiment, inorder to reduce the channel area of the portion 112 a of the otherdownstream duct 112 having a longer channel length, a contracted portion120 is provided on the upstream side of the other downstream duct 112.Thus, the channel area on the upstream side of the portion 112 a issmaller than the channel area on the downstream side of the portion 111b.

As illustrated in FIG. 9, a corner 121 a between the upstream duct 111and the one downstream duct 112 is formed to have a curved surface suchthat flue gas flows smoothly. Similarly, a corner 121 b between theportion 112 a and the portion 112 b of the other downstream duct 112 isformed to have a curved surface such that flue gas flows smoothly.

The blower fan 113 is provided outside the duct. The blower fan 113supplies outside air into the upstream duct 111 to mix flue gasdischarged from the gas turbine 10 a and the outside air, therebycooling the flue gas. The outside air from the blower fan 113 issupplied toward the outside air diffusion pipes 114. The blower fan 113is connected to the controller 60 similarly to the first embodiment.

The outside air diffusion pipes 114 diffuse the outside air suppliedfrom the blower fan 113 into the flue gas flowing through the upstreamduct 111. The outside air diffusion pipes 114 serve as members thatcreate channel resistance inside the upstream duct 111. In other words,the outside air diffusion pipes 114 function as diffusion membersconfigured to diffuse the outside air, and also function as channelresistance members that create channel resistance to the flue gas.

As illustrated in FIG. 7, the outside air diffusion pipes 114 areprovided in plurality at the bending portion formed between the portion111 a and the portion 111 b of the upstream duct 111. The outside airdiffusion pipes 114 are provided in two sections on both sides in thewidth direction orthogonal to the flowing direction of the flue gas. Thearrangement of the outside air diffusion pipes 114 illustrated in FIG. 7is an example, and the outside air diffusion pipes 114 are arranged asappropriate in accordance with the flowing state of the flue gas.

As illustrated in FIG. 8, the outside air diffusion pipes 114 are eachformed into a tubular shape, and are attached to the inner wall of theupstream duct 111 such that the longitudinal directions thereof are thevertical direction. The inner wall of the upstream duct 111 is providedwith annular protrusions 125 for respectively fixing both ends of theoutside air diffusion pipes 114, and the outside air diffusion pipes 114are inserted on the inner side of the protrusions 125. The outside airdiffusion pipes 114 are installed with a predetermined clearance fromthe inner wall of the upstream duct 111 in consideration of thermalelongation in the longitudinal direction caused by the heat of the fluegas.

In the outside air diffusion pipe 114, a plurality of ejection holes 126through which the outside air is ejected are formed so as to passthrough the wall thereof. The ejection holes 126 are provided along thelongitudinal direction of the outside air diffusion pipe 114 atpredetermined intervals so as to diffuse the outside air in the upstreamduct 111. As illustrated in FIG. 8, the ejection holes 126 formed in oneof adjacent outside air diffusion pipes 114 and the ejection holes 126formed in the other of the adjacent outside air diffusion pipes 114 areshifted in position such that ejected outside airs are not opposed toeach other. In other words, in the longitudinal direction, the ejectionholes 126 formed in one outside air diffusion pipe 114 are locatedbetween the ejection holes 126 formed in the other outside air diffusionpipe 114.

In such a distribution duct 110, when flue gas is discharged from thegas turbine 10 a, the flue gas flows through the upstream duct 111. Whenoutside air is ejected from the outside air diffusion pipes 114, theflue gas flowing through the upstream duct 111 is mixed with the outsideair, and the flue gas is cooled. The flue gas flowing through theupstream duct 111 flows toward the two downstream ducts 112. When theflue gas flows through the downstream ducts 112, the mixing of the fluegas and the outside air is promoted. The flue gas flowing through onedownstream duct 112 flows into one heat recovery steam generator 20. Theother downstream duct 112 has a channel area smaller than that of theone downstream duct 112 due to the contracted portion 120. Thus, theflow amount of the flue gas flowing through the other downstream duct112 is regulated with respect to the one downstream duct 112, and theflue gas flowing through the two downstream ducts 112 is equallydistributed.

Similarly to the first embodiment, the gas thermometers 117 are providedto the two downstream ducts 112. Control for the blower fan 113 by thecontroller 60 based on the gas thermometers 117 is the same as in thefirst embodiment, and hence description thereof is omitted.

Next, the case where a new gas turbine 10 a is provided at a locationillustrated in FIG. 11 is described. In FIG. 11, the new gas turbine 10a is provided on the side opposite to the existing two gas turbines 10across the two heat recovery steam generators 20, and is provided to belocated at the center between the two heat recovery steam generators 20in the direction in which the two heat recovery steam generators 20 arearranged.

As illustrated in FIG. 11 and FIG. 12, a distribution duct 130 includesan upstream duct 131, two downstream ducts 132, and a blower fan 133.The two downstream ducts 132 in the distribution duct 130 are providedwith two gas thermometers 137, respectively. The blower fan 133 and thegas thermometers 137 are connected to the controller 60.

The upstream duct 131 is connected to the gas turbine 10 a, and flue gasfrom the gas turbine 10 a flows inside the upstream duct 131. Theupstream duct 131 is formed into a rectangular tubular shape, and guidesthe flue gas toward the two downstream ducts 132. The upstream duct 131is formed to extend straight from the gas turbine 10 a toward a regionbetween the two heat recovery steam generators 20.

The two downstream ducts 132 branch off from the upstream duct 131 intotwo, and are connected to the two heat recovery steam generators 20. Thetwo downstream ducts 132 are each formed into a rectangular tubularshape, and communicate to the upstream duct 131 to guide flue gas fromthe upstream duct 131 toward the two heat recovery steam generators 20.

The upstream duct 131 and the two downstream ducts 132 are shaped todistribute the flue gas from the gas turbine 10 a equally to the twoheat recovery steam generators 20. Specifically, the upstream duct 131and the two downstream ducts 132 are shaped to be bilaterally symmetricabout the flowing direction of the flue gas discharged from the gasturbine 10 a. In the second embodiment, the two downstream ducts 132 arearranged to be inclined with respect to the flowing direction of theflue gas from the upstream duct 131 toward the two heat recovery steamgenerators 20. In this case, each of the downstream ducts 132 is formedsuch that the channel area is larger on the upstream side and becomessmaller toward the downstream side.

The blower fan 133 is provided at a branch portion where the upstreamduct 131 branches into the two downstream ducts 132. In other words, theblower fan 133 is provided at a corner formed by the two downstreamducts 132. The blower fan 133 supplies outside air in a directionopposed to the flowing direction of flue gas. Thus, the outside airsupplied from the blower fan 133 and the flue gas discharged from thegas turbine 10 a are opposed to each other to promote the mixing of theoutside air and the flue gas.

Similarly to the first embodiment, the gas thermometers 137 are providedto the two downstream ducts 132. Control for the blower fan 133 by thecontroller 60 based on the gas thermometers 137 is the same as in thefirst embodiment, and hence description thereof is omitted.

Next, a remodeling method of the GTCC power plant 100 according to thesecond embodiment is described with reference to FIG. 13. The GTCC powerplant 100 before remodeling is as illustrated in FIG. 1, and the GTCCpower plant 100 after remodeling is as illustrated in FIG. 6 and FIG.11.

As illustrated in FIG. 13, in the GTCC power plant 100 beforeremodeling, two gas turbines 10 and two heat recovery steam generators20 are connected by two ducts 17 (Step S21). In the GTCC power plant 100before remodeling, first, a new gas turbine 10 a is installed in avacant site in the GTCC power plant 100 (Step S21: gas turbineinstallation step). During the gas turbine installation step S21, theGTCC power plant 100 before remodeling can be continuously operated.

After the gas turbine installation step S21 is implemented, the two gasturbines 10 and the two ducts 17 are removed (Step S22: removal step).During the removal step S22, the GTCC power plant 100 is in theoperation suspended state. Subsequently, after the removal step S22 isimplemented, the distribution duct 110 or 130 is installed so as toconnect the new gas turbine 10 a and the existing two heat recoverysteam generators 20 to each other (Step S23: distribution ductinstallation step). At the distribution duct installation step S23, theupstream duct 111 or 131 in the distribution duct 110 or 130 isconnected to the gas turbine 10 a, and the two downstream ducts 112 or132 are respectively connected to the two heat recovery steam generators20. A pre-remodeling connection position between the heat recovery steamgenerator 20 and the duct 17 before remodeling and a post-remodelingconnection position between the heat recovery steam generator 20 and thedownstream ducts 112 or 132 after remodeling are different positions onopposite sides.

In this manner, also in the second embodiment, in the GTCC power plant100 after remodeling, the new gas turbine 10 a having gas turbineefficiency higher than that of the gas turbine 10 before remodeling isprovided. Even when the number of the new gas turbines 10 a is smallerthan the number of the heat recovery steam generators 20, the flue gasdischarged from the new gas turbine 10 a can be appropriatelydistributed and guided to two heat recovery steam generators 20 byproviding the distribution ducts 110 and 130.

As described above, according to the second embodiment, the gas turbineinstallation step S21 is performed before the removal step S22, andhence the existing two gas turbines 10 can be operated and thus the GTCCpower plant 100 can be operated until the removal step S22 is performed.The gas turbine installation step S21 is completed before the removalstep S22 is started, and hence the operation of the GTCC power plant 100can be restarted by performing the removal step S22 and the distributionduct installation step S23. Consequently, the operation suspensionperiod of the GTCC power plant 100 due to remodeling can be shortened.

Further, according to the second embodiment, the distribution duct 110or 130 can be connected to the post-remodeling connection positiondifferent from the pre-remodeling connection position. Consequently, thepost-remodeling connection position can be set to such a position as tofacilitate the routing of the distribution duct 110 or 130 and theconnection of the distribution duct 110 or 130. It should be noted thatwhen the heat recovery steam generator 20 is a vertical heat recoverysteam generator 20, the pre-remodeling connection position and thepost-remodeling connection position can be made different from eachother.

Further, according to the second embodiment, the blower fan 113 or 133is provided on the upstream side of the branch portion between theupstream duct 111 or 131 and the two downstream ducts 112 or 132, andhence the outside air and the flue gas can be mixed in the downstreamducts 112 or 132. Consequently, the mixing of the outside air and theflue gas can be further promoted.

Further, according to the second embodiment, the outside air suppliedfrom the blower fan 113 can be diffused in the distribution duct 110 bythe outside air diffusion pipes 114 to be supplied into the upstreamduct 111, and hence the mixing of the outside air and the flue gas canbe further promoted.

Further, according to the second embodiment, the contracted portion 120is provided in the distribution duct 110, and hence even when thedownstream ducts 112 have different channel lengths, the flue gasflowing through the two downstream ducts 112 can be equally distributed.

Further, according to the second embodiment, the outside air diffusionpipes 114 are provided in the distribution duct 110 to adjust the flowof the flue gas in the upstream duct 111, and hence a drift of the fluegas can be suppressed.

Further, according to the second embodiment, in the distribution duct130, the flue gas and the outside air are supplied so as to be opposedeach other, and hence the mixing of the outside air and the flue gas canbe promoted to suppress an uneven heat distribution of flue gas flowinginto the heat recovery steam generators 20.

Further, according to the second embodiment, in the distribution duct130, the upstream duct 131 and the two downstream ducts 132 have abilaterally symmetric shape, and hence the flue gas flowing through thetwo downstream ducts 132 can be equally distributed.

Third Embodiment

Next, a remodeling method of a GTCC power plant 100 according to a thirdembodiment is described with reference to FIG. 14. Also in the thirdembodiment, differences from the first and second embodiments aredescribed in order to avoid duplicated descriptions, and parts havingthe same configurations as in the first and second embodiments aredenoted by the same reference symbols. FIG. 14 is an explanatory diagramillustrating the remodeling method of the GTCC power plant according tothe third embodiment.

In the remodeling method of the GTCC power plant 100 in the thirdembodiment, in addition to the replacement of existing gas turbines 10with a new gas turbine 10 a, existing heat recovery steam generators 20are replaced with a new heat recovery steam generator 20 a.

The new heat recovery steam generator 20 a has higher efficiency forgenerating steam than the heat recovery steam generators 20 beforeremodeling. The new heat recovery steam generator 20 a is designed basedon the new gas turbine 10 a, and is thus capable of receiving flue gasdischarged from the new gas turbine 10 a.

Next, the remodeling method of the GTCC power plant 100 according to thethird embodiment is described with reference to FIG. 14. The remodelingmethod in the third embodiment is described based on the remodelingmethod in the first embodiment.

As illustrated in FIG. 14, in the GTCC power plant 100 beforeremodeling, two gas turbines 10 and two heat recovery steam generators20 are connected by two ducts 17 (Step S31). First, the two gas turbines10, the two ducts 17, and the two heat recovery steam generators 20 areremoved from the GTCC power plant 100 before remodeling (Step S32:removal step). After the removal step S32 is implemented, a new gasturbine 10 a is installed (Step S33: gas turbine installation step). Atthe gas turbine installation step S33, the new gas turbine 10 a isinstalled in a former site of the gas turbine 10 before remodelingremoved at the removal step S32.

After the removal step S32 is implemented, a new heat recovery steamgenerator 20 a is installed (Step S33: heat recovery steam generatorinstallation step). Also at the heat recovery steam generatorinstallation step S33, the new heat recovery steam generator 20 a isinstalled in a former site of the heat recovery steam generator 20before remodeling removed at the removal step S32.

Subsequently, after the new gas turbine 10 a and the new heat recoverysteam generator 20 a are installed, a duct 140 is installed so as toconnect the new gas turbine 10 a and the new heat recovery steamgenerator 20 a to each other (Step S33: duct installation step). At theduct installation step S33, the duct 140 is connected in order to guideflue gas from the single gas turbine 10 a to the single heat recoverysteam generator 20 a, which is substantially the same as the ducts 17used before remodeling.

As described above, according to the third embodiment, the new heatrecovery steam generator 20 a having high efficiency is installed inplace of the existing two heat recovery steam generators 20, and hencethe CC efficiency can be further improved. The number of the new gasturbines 10 a and the number of the new heat recovery steam generators20 a can be set to be equal to each other, and hence the flue gas is notrequired to be distributed. In this manner, it is only necessary to usethe existing steam turbine 30, replace the existing two gas turbines 10with the new gas turbine 10 a, and replace the existing two heatrecovery steam generators 20 with the new heat recovery steam generator20 a, and hence the CC efficiency can be further improved whilesuppressing increase in remodeling cost.

Fourth Embodiment

Next, a remodeling method of a GTCC power plant 100 according to afourth embodiment is described with reference to FIG. 15 to FIG. 17.Also in the fourth embodiment, differences from the first to thirdembodiments are described in order to avoid duplicated descriptions, andparts having the same configurations as in the first to thirdembodiments are denoted by the same reference symbols for description.FIG. 15 is an explanatory diagram illustrating an example of arrangementof a GTCC power plant after remodeling according to the fourthembodiment. FIG. 16 is a perspective view of a distribution duct in theGTCC power plant illustrated in FIG. 15. FIG. 17 is an explanatorydiagram illustrating a remodeling method of the GTCC power plantaccording to the fourth embodiment.

In the first embodiment, a new single gas turbine 10 a is installed inplace of two existing gas turbines 10, but in the fourth embodiment, anew single gas turbine 10 a is installed in place of one existing gasturbine 10 of the two existing gas turbines 10. In other words, in theGTCC power plant 100 after remodeling in the fourth embodiment, asillustrated in FIG. 15, a single existing gas turbine 10 and a singlenew gas turbine 10 a are provided. In the GTCC power plant 100 afterremodeling, a distribution duct 150 is provided in place of ducts 17.The new gas turbine 10 a to be provided in the GTCC power plant 100after remodeling is the same as in the first embodiment, and hencedescription thereof is omitted.

As illustrated in FIG. 15 and FIG. 16, the distribution duct 150includes two upstream ducts 151, a merging portion 152, two downstreamducts 153, a variable damper 73, and two blower fans 74. The twodownstream ducts 153 in the distribution duct 150 are each provided withone gas flowmeter 76 and one gas thermometer 77. The variable damper 73,the two blower fans 74, the gas flowmeters 76, and the gas thermometers77 are connected to the controller 60. The variable damper 73, the twoblower fans 74, the two gas flowmeters 76, and the two gas thermometers77 are the same as in the first embodiment, and hence descriptionthereof is omitted.

Of the two upstream ducts 151, one upstream duct 151 is connected to thenew gas turbine 10 a, and flue gas from the gas turbine 10 a flowsinside the one upstream duct 151, while the other upstream duct 151 isconnected to the existing gas turbine 10, and flue gas from the gasturbine 10 flows inside the other upstream duct 151. The two upstreamducts 151 are each formed into a rectangular tubular shape, and guidethe flue gas toward the merging portion 152.

The merging portion 152 is formed into a rectangular tubular shape, andthe flue gas from the gas turbine 10 a and the flue gas from the gasturbine 10 flow therethrough while being mixed. The merging portion 152guides the flue gas to the two downstream ducts 153.

The two downstream ducts 153 branch off from the merging portion 152into two, and are connected to the two heat recovery steam generators20. The two downstream ducts 153 are each formed into a rectangulartubular shape, and communicate to the merging portion 152 to guide fluegas from the merging portion 152 toward the two heat recovery steamgenerators 20.

The variable damper 73 is provided at the merging portion 152, andadjusts the distribution amount of flue gas to be distributed from themerging portion 152 to the two heat recovery steam generators 20.

As illustrated in FIG. 15 and FIG. 16, one upstream duct 151, themerging portion 152, and one downstream duct 153 are provided to extendstraight from the gas turbine 10 toward one heat recovery steamgenerator 20. The other upstream duct 151 is connected to merge towardthe one upstream duct 151. The other downstream duct 153 branches offfrom a connection portion between the merging portion 152 and the onedownstream duct 153. The other downstream duct 153 is the same as theother downstream duct 72 in the first embodiment, and hence descriptionthereof is omitted.

In such a GTCC power plant 100 after remodeling, the new gas turbine 10a is operated as a main gas turbine, and the existing gas turbine 10 isoperated as a sub gas turbine. Specifically, the allowable flow amountof flue gas that is allowed is designed in advance for the two heatrecovery steam generators 20, and hence in the case where the flue gasdischarged when the new gas turbine 10 a is operated does not reach theallowable flow amount of the two heat recovery steam generators 20, theexisting gas turbine 10 is operated. In other words, the existing gasturbine 10 is operated when the flow amount of the flue gas dischargedfrom the new gas turbine 10 a is insufficient with respect to theallowable flow amount of the two heat recovery steam generators 20. Inthis case, the existing gas turbine 10 is set such that the openingdegree of an inlet guide vane (IGV) configured to adjust the flow amountof air taken in by the compressor 11 is minimum. In the existing gasturbine 10, the opening degree of the IGV may be any opening degree aslong as an amount of flue gas corresponding to the shortage can besupplied.

Next, a remodeling method of a GTCC power plant 100 according to thefourth embodiment is described with reference to FIG. 17. The remodelingmethod in the fourth embodiment is described based on the remodelingmethod in the first embodiment.

As illustrated in FIG. 17, in the GTCC power plant 100 beforeremodeling, two gas turbines 10 and two heat recovery steam generators20 are connected by two ducts 17 (Step S41). First, one gas turbine 10and the two ducts 17 are removed from the GTCC power plant 100 beforeremodeling (Step S42: removal step). After the removal step S42 isimplemented, a new gas turbine 10 a is installed (Step S43: gas turbineinstallation step).

Subsequently, after the new gas turbine 10 a is installed, thedistribution duct 150 is installed so as to connect the new gas turbine10 a and the existing gas turbine 10 to the existing two heat recoverysteam generators 20, respectively (Step S43: duct installation step).

As described above, according to the fourth embodiment, a new gasturbine 10 a having high efficiency is installed in place of oneexisting gas turbine 10 while leaving the other one existing gas turbine10, and hence CC efficiency can be improved. Even when the new gasturbine 10 a and the existing gas turbine 10 are used in combination,the distribution duct 150 merges the flue gas and thereafter distributesthe merged flue gas, and hence the flue gas can be supplied to existingtwo heat recovery steam generators 20. By using the new gas turbine 10 aand the existing gas turbine 10 in combination, the flow amount of fluegas to be supplied to the existing two heat recovery steam generators 20can be prevented from being insufficient. Consequently, the existing twoheat recovery steam generators 20 can produce an amount of steamequivalent to that before remodeling, and the output decrease of thesteam turbine 30 can be suppressed. In this manner, by using theexisting two heat recovery steam generators 20 and the existing steamturbine 30 and replacing one existing gas turbine 10 with the new gasturbine 10 a, the CC efficiency can be improved while suppressingincrease in remodeling cost. Specifically, the total of output of thenew gas turbine 10 a and output of the existing gas turbine 10 can beincreased while maintaining the output of the steam turbine 30 beforeand after remodeling, and hence the output of the entire GTCC powerplant 100 can be increased.

EXPLANATIONS OF LETTERS OR NUMERALS

G1, G2 generator

La air introduction line

Lb compressed air supply line

Lc combustion gas supply line

Ld fuel supply line

L0 heat transfer pipe

L1 main steam line

L2 discharge line

L3 condensate line

L4 flue gas line

10 gas turbine

11 compressor

12 combustor

13, 31 turbine

14, 32 rotor

15 drive shaft

17, 140 duct

20 heat recovery steam generator

30 steam turbine

40 condenser

50 water supply pump

60 controller

70, 110, 130, 150 distribution duct

71, 111, 131, 151 upstream duct

72, 112, 132, 153 downstream duct

73 variable damper

74, 113, 133 blower fan

76 gas flowmeter

77, 117, 137 gas thermometer

81 turning shaft

82 blade

100 GTCC power plant

114 outside air diffusion pipe

120 contracted portion

125 protrusion

126 ejection hole

152 merging portion

1. A remodeling method of a combined cycle plant, the combined cycleplant comprising: a plurality of gas turbines; a plurality of heatrecovery steam generators that are provided corresponding to number ofthe gas turbines and configured to recover heat of flue gas dischargedfrom the gas turbines and produce steam by the recovered heat; aplurality of ducts configured to guide the flue gas from the gasturbines toward the respective heat recovery steam generators; and asteam turbine configured to be rotationally driven by the steam producedby the heat recovery steam generators, the remodeling method comprising:removing the gas turbines and the ducts; installing, in place of the gasturbines, a new gas turbine that is higher in efficiency and smaller innumber than the gas turbines; and installing, in place of the ducts, adistribution duct configured to distribute and guide the flue gas fromthe new gas turbine to the heat recovery steam generators.
 2. Theremodeling method of a combined cycle plant according to claim 1,wherein the installation of the new gas turbine is performed after theremoval, and the installation of the new gas turbine includes installingthe new gas turbine in a former site of the gas turbines removed in theremoval.
 3. The remodeling method of a combined cycle plant according toclaim 1, wherein the installation of the new gas turbine is performedbefore the removal, and the installation of the new gas turbine includesinstalling the new gas turbine in a vacant site.
 4. The remodelingmethod of a combined cycle plant according to claim 3, wherein each ofthe heat recovery steam generators is a vertical heat recovery steamgenerator in which the flue gas flows from a lower side to an upper sidein a vertical direction, and in the installation of the distributionduct, pre-remodeling connection positions at which the ducts beforeremodeling are connected to the heat recovery steam generators andpost-remodeling connection positions at which the distribution ductafter remodeling is connected to the heat recovery steam generators aredifferent positions.
 5. The remodeling method of a combined cycle plantaccording to claim 1, wherein the removal includes further removing theheat recovery steam generators, and the remodeling method furthercomprises: installing, in place of the heat recovery steam generators, anew heat recovery steam generator provided corresponding to number ofthe new gas turbines; and in place of the installation of thedistribution duct, installing a duct configured to guide the flue gasfrom the new gas turbine to the new heat recovery steam generator. 6.The remodeling method of a combined cycle plant according to claim 1,wherein the distribution duct installed in the installation of thedistribution duct is provided with a cooling device configured to coolthe flue gas discharged from the new gas turbine.
 7. The remodelingmethod of a combined cycle plant according to claim 1, wherein thecombined cycle plant is a multi-shaft combined cycle plant in which arotating shaft of the gas turbine and a rotating shaft of the steamturbine are separate from each other.
 8. A remodeling method of acombined cycle plant, the combined cycle plant comprising: a pluralityof gas turbines; a plurality of heat recovery steam generators that areprovided corresponding to number of the gas turbines and configured torecover heat of flue gas discharged from the gas turbines and producesteam by the recovered heat; a plurality of ducts configured to guidethe flue gas from the gas turbines toward the respective heat recoverysteam generators; and a steam turbine configured to be rotationallydriven by the steam produced by the heat recovery steam generators, theremodeling method comprising: removing one or more of the gas turbinesand removing the ducts while leaving at least one of the gas turbines;installing, in place of the removed gas turbines, a new gas turbine thatis higher in efficiency than the removed gas turbines; and installing,in place of the ducts, a distribution duct configured to merge the fluegas from the left gas turbine and the flue gas from the new gas turbinetogether, and distribute and guide the merged flue gas to the heatrecovery steam generators.
 9. A distribution duct for connecting one ormore gas turbines to a plurality of heat recovery steam generators thatare larger in number than the gas turbines, the heat recovery steamgenerators being configured to recover heat of flue gas discharged fromthe gas turbines and produce steam by the recovered heat, thedistribution duct comprising: an upstream duct which is connected to thegas turbine and in which the flue gas from the gas turbine flows; and aplurality of downstream ducts which communicate to the upstream duct,branch off from the upstream duct, and are connected to the heatrecovery steam generators to distribute the flue gas flowing through theupstream duct.
 10. The distribution duct according to claim 9, furthercomprising a cooling device configured to cool the flue gas from the gasturbine, wherein the cooling device is a blower fan that suppliesoutside air into the distribution duct.
 11. The distribution ductaccording to claim 10, wherein the blower fan supplies the outside airin a direction opposite to a flowing direction of the flue gas.
 12. Thedistribution duct according to claim 10, wherein the blower fan isprovided on an upstream side of a branch portion at which the upstreamduct branches into the downstream ducts.
 13. The distribution ductaccording to claim 10, further comprising a diffusion member configuredto diffuse the outside air supplied from the blower fan inside thedistribution duct.
 14. The distribution duct according to claim 9,further comprising a cooling device configured to cool the flue gas fromthe gas turbine, wherein the cooling device is an ejector configured totake in outside air by the flue gas flowing inside the distributionduct.
 15. The distribution duct according to claim 9, wherein theupstream duct and the downstream ducts are shaped to distribute the fluegas from the gas turbine equally to the heat recovery steam generators.16. The distribution duct according to claim 15, wherein the upstreamduct and the downstream ducts are shaped to be bilaterally symmetricabout a flowing direction of the flue gas discharged from the gasturbine.
 17. The distribution duct according to claim 15, wherein thedownstream ducts have different channel lengths from the upstream ductto the heat recovery steam generator, and a channel area of a channelthrough which the flue gas flows from the upstream duct into one of thedownstream ducts having a larger channel length is smaller than achannel area of a channel through which the flue gas flows from theupstream duct into one of the downstream ducts having a shorter channellength.
 18. The distribution duct according to claim 9, furthercomprising a variable damper configured to adjust a distribution amountof the flue gas to be distributed from the gas turbine to the heatrecovery steam generators.
 19. The distribution duct according to claim9, further comprising a channel resistance member configured to adjust achannel resistance in at least one of the upstream duct and thedownstream ducts.
 20. A distribution duct for connecting a plurality ofgas turbines to a plurality of heat recovery steam generators, the heatrecovery steam generators being configured to recover heat of flue gasdischarged from the gas turbines and produce steam by the recoveredheat, the distribution duct comprising: a plurality of upstream ductswhich are connected to the gas turbines and in which the flue gas fromthe gas turbines flows; a merging portion which communicates to theupstream ducts and at which the flue gases flowing through the upstreamducts merge; and a plurality of downstream ducts which communicate tothe merging portion, branch off from the merging portion, and areconnected to the heat recovery steam generators to distribute the fluegas flowing through the merging portion.
 21. A combined cycle plant,comprising: one or more gas turbines; the distribution duct according toclaim 9, which is connected to the gas turbine; a plurality of heatrecovery steam generators that are connected to the distribution ductand larger in number than the gas turbine; and a steam turbineconfigured to be rotationally driven by steam produced by the heatrecovery steam generators.
 22. A combined cycle plant, comprising: aplurality of gas turbines having different efficiencies; thedistribution duct according to claim 20, which is connected to the gasturbines; a plurality of heat recovery steam generators connected to thedistribution duct; and a steam turbine configured to be rotationallydriven by steam produced by the heat recovery steam generators.